Sonar altimeter measurements of bed level change were made in conjunction with instantaneous measurements of sea surface elevation and currents at a fixed position in a saturated surf zone (water depths less than 1 m). Two types of bed behavior were observed, classified as “progressive,” where mean bed level showed a steady increase or decrease with time, and “oscillatory,” where the bed level took a periodic motion (amplitudes 0.5–1.5 cm, periods 10–30 min). “Mixed” combinations of the two behaviors were also observed. Comparisons between bed behavior and a wave-based mobility number parameter (Ψ) observed oscillatory beds for Ψ < 40 and mixed behavior for 40 < Ψ < 80, suggesting that bed level oscillations were due to the presence of small-scale migratory bedforms (ripples). Bed oscillations were suppressed with increased wave energy, such that progressive bed behavior was observed when 80 < Ψ. The increase in mobility numbers associated with progressive beds was due to the presence of an energetic infragravity component (Eu_ig/Eu_i > 1 and Eu_ig > 0.05 m²s⁻²) and strong mean current (>0.1 ms⁻¹). A fractal analysis of the bed level time series was used to test the hypothesis that the process of ripple migration is nonlinear (“self-organised”) rather than a direct response to variations in the forcing component. For low wave energy conditions, when ripples were observable (oscillatory and mixed time series), values of the Local Hurst Exponent (0 < H_L < 1) suggested fractal behavior at ripple migration timescales, indicating that the process by which ripples migrate is nonlinear and is allowed to flourish when the hydrodynamic forcing is weak.